Chemically thickened polyester resin

ABSTRACT

The viscosity of unsaturated polyester resins formed by mixing the condensation polymers of unsaturated dicarboxylic acids and dihydric alcohols in ethylenically unsaturated copolymerizable monomers may be greatly increased by adding (1) a mixture of calcium oxide and either calcium hydroxide or magnesium oxide, and (2) an organic acid selected from the group consisting of benzoic acid, cyclohexane carboxylic acid, cinnamic acid and phydroxybenzoic acid to the unsaturated polyester resins. The viscosity of the composition is initially low enough so that fibrous reinforcements can be impregnated with the resin composition and the low viscosity permits the resin to wet the fibers, thereafter the viscosity of the resin increases and the fibrous reinforced mass loses its tackiness and can be easily stored and handled.

United States Patent 1 Baum et al. 1 Jan. 30, 1973 I 541 CHEMICALLYTHICKENED 3,536,642 10 1970 Williger ..260/22 POLYESTER RESIN PrimarExaminer-William H. Short [75] Inventors: Melvin E. Baum, Monroevrlle,Pa Asst-stair Examiner }g A Nielsen John Hanon Madelra OhmAttorney-Oscar B. Brumback et a1.

[73] Assignee: Koppers Company, Inc. [57] ABSTRACT l22 Filed: i n V U HV The viscosity of unsaturated polyester resins formed pp No: 177,779 bymixing the condensation polymers of unsaturated Related U.S. ApplicationData dicarboxylic acids and dihydric alcohols in ethylenicallyunsaturated copolymerizable monomers may be greatly increased by adding(1) a mixture of calcium oxide and either calcium hydroxide or magnesiumoxide, and (2) an organic acid selected from the group consisting ofbenzoic acid, cyclohexane carboxylic acid, cinnamic acid andp-hydroxybenzoic acid to the unsaturated polyester resins. 1

The viscosity of the composition is initially low enough so that fibrousreinforcements can be impregnated with the resin composition and the lowviscosity permits the resin to wet the fibers, thereafter the viscosityof the resin increases and the fibrous reinforced mass loses itstackiness and can be easily stored and handled.

5 Claims, 2 Drawing Figures [62] Division of Ser. No. 28,600, April 15,1970, Pat. No.

[52] U.S. Cl. ..260/865,l61/195, 161/233, 260/40 R [51] Int. Cl ..C08f43/02 [58] Field of Search ..260/865, 40 R [56] References Cited UNITEDSTATES PATENTS 3,219,604 11/1965 Fischer .,..260/22 3,390,205 6/1968Schnell et al.. .....260/865 3,431,320 3/1969 Baum et al. ..260/865UNSATURATED 4,,5 ETHYLENICALLY POLYESTER UNSATURATED MoNoMER ORGANICACCELERATOR UNSATURATED POLYESTER RESIN CALCIUM OXIDE THICKENERCHEMICALLY THICKENED POLYESTER RESIN This is a division, of applicationSer. No. 28,600, filed Apr. 15,1970, now U.S. Pat. No. 3,637,911.

BACKGROUND OF THE INVENTION This invention relates in general topolyester resin compositions having a thickening agent therein.

United States Letters Patent No. 3,219,604, Polyester Resin CompositionModified by Monocarboxylic Acid and Metallic Bridging Agent, describesthat polyester resin compositions can be thickened by heating the resinswith either magnesium oxide, aluminum oxide or calcium oxide and analiphatic monocarboxylic acid having from six to 24 or more carbon atomsin the chain to a temperature of 140 to 250F. for a period of from 5minutes to 40 hours so long as a large quantity of inhibitor is presentto prevent polymerization. An inherent tendency, of

course, is for the polyester resin to partially cure to a gel state atelevated temperatures.

US. Pat. No. 3,465,061, Unsaturated Polyester Resin Compositions Havinga Thickening Agent Therein, describes a product which is initially thinbut within a day becomes thick, without the application of heat, formedby adding to an unsaturated polyester resin an oxide of a Group Il-Ametal and an anhydride of a cyclic hydrocarbon. According to US. Pat.No. 3,465,061, maleic anhydride and phthalic acid are not particularlyeffective for thickening the polyester resin; the anhydrides of cyclichydrocarbons must be used.

There are some other thickening systems that do not require theapplication of heat to produce the thickening effect. US. Pat. No.3,431,320, Polyester Resin Composition Having a Thickening Agent Thereindescribes that the chemical thickening of polyester resins by theaddition of Ca(OH) or MgO can be greatly enhanced by the addition ofCaO. According to US. Pat. No. 3,431,320, despite a rapid high viscositybuild-up, the pot life of the resin can be extended. This findingenabled sheets to be made, for example, such as fibrous mats impregnatedwith the polyester resin wherein the resin thickened to yield sheetswhich were capable of being stacked, with release agents therebetween,for a period of time without the sheets flowing, i.e., changingdimensions an undesirable amount or the glass fibers separating from theresin.

SUMMARY OF THE INVENTION It has now been discovered that the thickeningeffect described in U.S. Pat. No. 3,431,320 can be greatly acceleratedby the addition of certain monocarboxylic acids, each having a sixcarbon ring member in its structure, to the unsaturated polyester resincontaining a mixture of calcium hydroxide or magnesium oxide and calciumoxide. The thickening is accelerated without the application of heat tothe composition and, therefore, large amounts of polymerizationinhibitors do not have to be added to the composition to preventpremature curing to a gelation state.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates generally in the blockdiagram the resinous composition.

FIG. 2 illustrates a layer made in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the invention aresin composition which greatly increases in viscosity is produced froman unsaturated polyester resin which includes an unsaturated polyesterformed by condensing at least one dicarboxylic acid containinga,fl-ethylenic unsaturation with a dihydric alcohol and an afi-ethylenically unsaturated copolymerizable monomer, preferably a styreneor vinyl-type monomer, by the addition to the resin of a thickeningagent in an amount sufficient to increase the viscosity of thecomposition after a period of time, said thickening agent consisting ofa mixture of (1) calcium oxide, CaO, and (2) either calcium hydroxide,Ca(OH or magenesium oxide, MgO, and an effective amount of amonocarboxylic acid having a six carbon ring member in its structure andselected from the group consisting of:

benzoic acid cyclohexane carboxylic acid cinnamic acid andp-hydroxybenzoic acid The amount of the calcium oxide, calcium hydroxideand magnesium oxide added to the unsaturated polyester resin may varysomewhat depending uponthe amount of viscosity build-up desired. It hasbeen found, however, that at least 0.5 percent by weight of calciumoxide based on the total weight of the polyester resin must be present.It has also been found that the magnesium oxide or calcium hydroxidemust be present in an amount by weight of at least 0.5 percent based onthe weight of the polyester resin. Larger amounts of calcium oxide,calcium hydroxide or magnesium oxide I may be used; the large amountsact more as fillers and are unnecessary to produce the rapid chemicalthickening when the organic accelerators are used in accordance withthis invention. Amounts of the monocarboxylic acids as low as 0.25percent by weight based on the weight of the polyester resin areeffective in producing the thickening accelerating effect of theinvention. Generally, amounts of from 0.5 to 2.0 percent ingdicarboxylic acids with dihydric alcohols. Approxi- I mately equimolarproportions of the dicarboxylic acids and dihydric alcohols are used. Toprovide unsaturation within the polyester, at least a portionof thedicarboxylic acids contain ethylenic unsaturation. Maleic and fumaricacids are common examples of ethylenically unsaturated dicarboxylicacids. Mixed with these acids may be dicarboxylic acids-that aresaturated normal aliphatic acids such as adipic acid, succinic acid, or

the like, or that'are aromatic dicarboxylic acids such as phthalic acid,isophthalic acid or the like as well as halogenated derivatives of sucharomatics acids, for instance, tetra-chlorophthalic anhydri'de.

, Illustrative of the dihydric alcohols used for the production ofpolyesters are ethylene glycol, propylene glycol, 1,2-butanediol,1,3-butanediol, 1,4-butanediol, diethylene glycol, polypropylene glycol,2,2-dimethyl- 1,3-pfopanediol, l,4-cyclohexane dimethanol and ad ductsor reaction products of alkylene oxides with 2,2- bis(4-,hydroxyphenylene) propane (Bis-phenol A).

To produce the polyester resin, the unsaturated polyester is dissolvedin an a,B-ethylenically unsaturated monomer. The amount of monomer usedgenerally is about 20-70 percent (and preferably 30-60 percent) byweight of the total polyester resin. If the percentage of monomer is toolow the viscosity of the finalresin will be initially too high for goodwetting of the glass fibers and the amount of cross linking of the finalproduct will be small so that characteristics such as deflectiontemperature and tensile strength are not that which are'normallydesired.On the other hand, too much monomer may cause anundesirable shrinkageduring'curingand'an undesirable exotherm during curing'. Preferably30-60 percent of monomer by weight is used. The unsatur atedpolyester'resin (polyester and monomer) is then cured by'initiating afree radical polymerization between the ethylenically unsaturated 1monomer and the unsaturated polyester at the 0,3-

ethylenic double bonds in they polyester. This copolyr'neri zation iscommonly initiated by addition of a free radical generating catalystfollowed by heating. The polyester and monomer compositions of thepolyester resin f copolymerize to form a cross-linked thermoset resin.

Illustrative of the copolymerizable ethylenically unsaturated, monomersare styrene, a-methylstyrene, chlorostyrene, jvinyl' toluene, divinylbenzene, diallylphthalate, methyl methacrylate and the like.

- Examplesof the free radical generating catalysts are peroxidecatalysts such as I benzoyl peroxide, methylethyl ketone peroxide,cumene hydroperoxide,

and thelike. Other free 'radicalgenerating catalysts.

may also be used as, for example: 2,2'-azobisisobutyronitrile.Preferably the catalyst system selected is onewhich is inactive at roomtemperature since the inmade from the condensation reaction ofapproximately equi molar proportions of the dihydric alcohols anddicarboxylic acids are dissolved in, by difference, 20-70, andpreferably, 30-60, parts of one of the 01,3- ethylenically unsaturatedmonomers, i.e., the resin is the polyester dissolved in the monomer. Tothe parts by weight of the resin are added a mixture of at least 0.5parts by weight of calcium oxide and 0.5 parts by weight of eithercalcium hydroxide or magnesium oxide and an effective amount of amonocarboxylic acid selected from the group consisting of benzoic acid,cyclohexane carboxylic acid, cinnamic acid and phydroxybenzoic acid.Tl-le mass is mixed with a conventionalmixer, for example a Cowlessmixer, until the mass is thoroughly mixed, usually a matter of minutes.Then the catalyst is added and mixed into the mass.

Conventional fillers, pigments and mold release agents can be mixed intothe polyester resin at anytime during the production of the chemically.thickened resin. Generally, however, they are added prior to theaddition of the thickener.

In use a layer of the composition to which the thickener, filler,pigment and catalyst have been-added is poured onto a film ofpolyethylene which is moving past the pouring point. A layer of choppedglass is then mass of resin and glass fiber is chosen according to theproperties desired of the polyester after it has been'cured. As theweight of glass is increased the strength of the cured polyesterincreases. The surface appearance of the cured-polyester,

however, suffers as the weight of glass inthe cured polyester increases.Generally, the glass makes up 15-30 percent of the mass of resin andglass fibers. The sheets are then passed between two pressure rollerswith the polyethylene film in contact with the rollers to squeeze theresin layer into'the fiber layer to enable the resin to penetrate thechopper glass layer and wet the glass fibers. The viscosity of the resinis initially sufficiently low to wet the glass fibers and to allow theresin layers to blend together. However, theviscosity of :the resincomposition rapidly increases and the mass of resin andglass'fibersloses its tackiness. Accordingly, workmen can remove thepolyethylenefilm and stack the layers of composition and fiber mass after a periodof chopped glass betweenthe two layers of only one to two days. Theindividual layers may be removed from the stack at will and placed in amold for molding in accordance with conventional molding techniques.

The invention will be further understood by referring to the blockdiagram of FIG. 1 and the following exam- Example I To illustrate thepractice of this invention aliquots were taken from a commerciallyavailable unsaturated polyester resin sold under the trademark KOPLACGrade 2000 (made by the condensation of 1.0 mole each of maleicanhydride and phthalic anhydride with approximately 2.0 mole ofpropylene glycol.) The resin was analyzed to contain 40 percent styreneand 60 percent polyester and to have an acid number of about 15.8. To100 parts of each aliquot was added 3.2 parts of calcium oxide and 2.8parts of calcium hydroxide and, except for aliquot (1 there was added0.7 parts of a monocarboxylic acid in accordance with the inven tion.The viscosities in each case through this specification were measuredwith a Brookfield Syncrolectric Viscometer (Model LVT up to 2 millioncentipoise and Model HBT up to 64 million centipoise.) The results aretabulated below:

TABLE 1 Ali- Acid 1 2 7 2 3 2 4 quot day days weeks weeks mos. mos.

(1) None 85 190 360 (2) Benzoic 2850 3850 4400 5400 6700 15700 (3)Cinnamic 183 690 500 380 600 1800 (4) p-Hydroxybenzoic 76 123 215 210345 470 (5) Cyclohexane H Carboxylic 3400 5900 5700 5100 10200 64000From the foregoing it is evident that the benzoic acid and cyclohexanecarboxylic acid are the most effective in promoting greater thickening.It will be noted, however, that with the calcium hydroxide/calcium oxidethickening agents previously known, all of the monocarboxylic acids setout in the table were effective in accelerating the thickening.

Example 11 To 5 aliquots of another commercially available unsaturatedpolyester resin, KOPLAC Grade 6101 (made by condensing 1.0 moleisophthalic acid and 1.4 mole maleic anhydride with 0.8 mole dipropyleneglycol and about 1.7 mole of propylene glycol), analyzed as containing70 percent polyester and percent styrene, was added enough monomericstyrene to dilute the resin to a 60/40, polyester/styrene, ratio. Theacid number of these diluted aliquots was analyzed to be 13.2. To 100parts of each of the diluted aliquots was added 3.2 parts calcium oxideand 2.9 parts calcium hydroxide and, except for aliquot (1), thespecified parts of benzoic acid as set out below:

TABLE 11 Table 11 illustrates the accelerating effect of benzoic acid onthe thickening effect of the previously known calcium hydroxide/calciumoxide thickening agents. It is evident from the table that theaccelerating effect increases as the concentration of acid in theunsaturated polyester resin increases. Similar results were obtainedExample 111 To parts of each of six aliquots of the "00111111131 7cially available KOPLAC Grade 6101 unsaturated polyester resin describedin Example 11 (70/30 polyester/styrene ratio and having an acid numberof 15.4) were added, as set out below, the specified parts of calciumoxide, calcium hydroxide and, except for aliquots (l) and (2),cyclohexane carboxylic acid.

TTTABLE III Ali- 'Pa'ik" Parts Parts quot cyelocalcium calcium hexane oide hydroxide Visc0s ity in cps X10 carboxxylic acid 1 7 2 l 2 day daysweeks month months From the foregoing it is evident that theaccelerating effect of the invention can be controlled by varying theamounts of calcium oxide and calcium hydroxide or magnesium oxide addedto the unsaturated polyester resin containing an effective amount of themonocarboxylic acid. Generally, however, it is not necessary for thetotal amount of calcium oxide and calcium hydroxide or magnesium oxidepresent in the thickened composition to exceed 6 percent by weight toachieve a sufficient rapid viscosity thickening to produce the moldablelayers of the invention.

A flexible layer, suitable for matched-die molding 50 was produced fromthe composition of the invention by hydroxide and 0.75 parts of benzoicacid. After thoroughly mixing the aliquot, the resin was poured onto amoving sheet of polyethylene film having a width of 24 inches. A layerof strands of 1 inch length of Owens-Corning Type 415 fiber glass weredropped onto the moving resin-coated film, across the width of the film.The resin was also poured onto a second film of polyethylene and theresin-coated sheet flipped over. The resin is sufficiently thick toprevent the resin from dripping off of the film.

The amount of chopped glass dropped onto the resin-coated film wasapproximately 20 percent weight based on the final glass-resin system.The resin composition face of the second filmwas brought into contactwith the glass-resin composition face of the first film and passedbetween pressure rollers with the polyethylene film in contact with therollers so that the layers were squeezed to cause the resin to penetratethe layer of chopped glass and wet the glass fibers. Several days laterthe layer of resin and glass was placed in a matched-die mold and heatedto a temperature of 280-300F. for approximately three minutes. Removedfrom the mold the cured article had a smooth surface appearance and goodhardness.

A layer of the type described above is illustrated in FIG. II. The layeris flexible, moldable, storable and non-tacky within a period of timeafter formation of the layer.

Thus, the chemically thickened resins of the invention have an initialviscosity low enough to insure proper wetting of glass fibers coatedwith the resins. The viscosities of the resin greatly increase within aspaced period of time thereafter, whereby mats of the coated glass andfibers lose their tackiness and can be easily handled and stored.

What is claimed is:

1. An unsaturated polyester resin composition which greatly increases inviscosity within a period of time after formation of the compositionwhich comprises:

a. an unsaturated polyester formed by condensing at least onedicarboxylic acid containing 01,3-

ethylenic unsaturation with a dihydric alcohol;

b. an a,B-ethylenically unsaturated copolymerizable monomer and;

c. a thickening agent in an amount sufficient to increase the viscosityof the composition after a period of time, said thickening agentconsisting of:

l. a mixture of at least 0.5% by weight based on the weight of theunsaturated polyester resin of calcium oxide and at least 0.5 percent byweight of compound selected from the class consisting of calciumhydroxide and magnesium oxide, and

2. p-hydroxybenzoic acid in an amount of from 0.25 to 2.0 percent byweight based on the weight of the unsaturated polyester resin.

2. The composition of claim 1 wherein the unsaturated polyester ispresent in an amount of from 20 to 70 percent by weight based on thetotal weight of the unsaturated polyester and a,B-ethylenicallyunsaturated monomer.

3. The composition of claim 1 wherein the monocarboxylic acid is presentin an amount of from 0.25 to 2.0 percent weight based on the weight ofthe unsaturated polyester resin.

4. The composition of claim 1 wherein the mixture of the thickeningagent includes at least 0.5 percent by weight based on the weight of thepolyester resin of calcium oxide and at least 0.5 percent by weight ofcalcium hydroxide.

5. The composition of claim 1 wherein the mixture of the thickeningagent includes based on the weight of the polyester resin at least 0.5percent of calcium oxide

1. An unsaturated polyester resin composition which greatly increases inviscosity within a period of time after formation of the compositionwhich comprises: a. an unsaturated polyester formed by condensing atleast one dicarboxylic acid containing Alpha , Beta -ethylenicunsaturation with a dihydric alcohol; b. an Alpha , Beta -ethylenicallyunsaturated copolymerizable monomer and; c. a thickening agent in anamount sufficient to increase the viscosity of the composition aftEr aperiod of time, said thickening agent consisting of:
 1. a mixture of atleast 0.5% by weight based on the weight of the unsaturated polyesterresin of calcium oxide and at least 0.5 percent by weight of compoundselected from the class consisting of calcium hydroxide and magnesiumoxide, and
 2. p-hydroxybenzoic acid in an amount of from 0.25 to 2.0percent by weight based on the weight of the unsaturated polyesterresin.
 2. The composition of claim 1 wherein the unsaturated polyesteris present in an amount of from 20 to 70 percent by weight based on thetotal weight of the unsaturated polyester and Alpha , Beta-ethylenically unsaturated monomer.
 3. The composition of claim 1wherein the monocarboxylic acid is present in an amount of from 0.25 to2.0 percent weight based on the weight of the unsaturated polyesterresin.
 4. The composition of claim 1 wherein the mixture of thethickening agent includes at least 0.5 percent by weight based on theweight of the polyester resin of calcium oxide and at least 0.5 percentby weight of calcium hydroxide.